In a human, assuming no mutations, is it possible to have a child with this phenotype, given the phenotype of the parents?

The mother, Alice, has black hair and brown eyes. The father, Bob, has red hair and green eyes. The child, Clare, has green eyes and black hair.

From what I know of genetics, and experimentation using a simplified model, called the 'Genetic Heredity Calculator', this should not be possible.

Being green eyed is apparently a 10%. chance, however resulting in a black-haired child isn't supposed to be possible.

Of course, my understanding of genetics is far from complete. Is it possible, and if so, what is the likelihood that this is the result, knowing nothing else of the parents' genetics, aside from them being caucasian British?

My question revolves around Alice, who has hair well within the commonly perceived range of 'black', which I here define as <7 lightness in HSL, having a child with Bob, a redheaded man, which I shall define as a man whose hair colour in hex is greater than 3:2 r:g, and >30 Lightness in HSL.

Such precision is not required, but exists to put the question in context.

  • $\begingroup$ I don't think our understanding of the genetic basis of hair and eye colour are good enough to give you probabilities for offspring to have certain combinations or shades of colours. The possible phenotypic range for these traits always contains at the very least the two parental phenotypes. One parent has black hair - why would it be impossible for a child to have black hair? $\endgroup$ – Armatus Feb 18 '18 at 16:30
  • $\begingroup$ I think I found the tool you refer to and it's certainly not to be taken seriously. It output 100% brown hair colour for children of one black-haired and one blonde-haired parent. My parents are that exact combination, and they have one blonde, two brown-haired and one black-haired child. $\endgroup$ – Armatus Feb 18 '18 at 16:35
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    $\begingroup$ many genes code for hair color and eyes, not just one. and the chromosomes can be split into 2-3 pieces and jumbled. $\endgroup$ – aliential Feb 18 '18 at 18:14

unlikely but possible

Eyes. As you already indicated green eyes are possible just through recombination, in fact lighter color eyes are always possible due to mutation. All the major eye colors use the same pigment anyway, it is just amount and depth that varies, so it is not discrete genetic trait meaning ballparking is the best you can do.

Hair. All the necessary genes are present in the parent pool so it is possible. Brown and black hair are just different levels of the same pigments not due to the absence of a pigment like red hair. There is also more than one combination to get both black and brown hair. If both parents lacked the same pigment (both redheads) it would prevent black or brown hair but this is not the case so black hair is indeed possible, unlikely but possible. Worse hair color genes can be hidden by dominate ones so you can't even guess the parents genes so any estimate will be just guesswork.

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  • $\begingroup$ Do you have any kind of rough estimate as to how likely it would be? $\endgroup$ – Piomicron Feb 22 '18 at 17:22
  • $\begingroup$ not aa good one the genetics of hair color is not well understood the physiology of it allows for it however. black and brown are caused by the same pigments so for a really rough back of the envelop you could say half the chance of brown hair, so around 25%, $\endgroup$ – John Feb 22 '18 at 18:54

The genetics of eye colour and hair colour is not easy enough so that we can answer. There are two main issues. 1) The traits in question are quantitative (takes continuous values) and not discrete which makes the expression "brown eyes" a little inaccurate and undefined. 2) Those traits are polygenic traits. In other words, there are a lot of loci that affect eye colour and hair colour and pretty much everything end up being possible.

So, yes it is possible, although it would be more likely that Claire has brown eyes.

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  • $\begingroup$ Updated for precision $\endgroup$ – Piomicron Feb 15 '18 at 23:43
  • $\begingroup$ Is it possible for Claire to have 'black' hair? $\endgroup$ – Piomicron Feb 17 '18 at 12:14
  • $\begingroup$ @Armatus Yes, definitely. Sorry that was a mistake. Thanks for pointing that out $\endgroup$ – Remi.b Feb 18 '18 at 16:37
  • $\begingroup$ Roughly how likely is having the correct hair colour? $\endgroup$ – Piomicron Feb 22 '18 at 17:23
  • $\begingroup$ 1) Your follow-up question is partly undefined. We would need an exact measurement of what you call "black" and "red" 2) I would not know anyway and I don't know if there is any study on that. $\endgroup$ – Remi.b Feb 22 '18 at 17:57

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